(A) Field of the Invention
The present invention relates to an electromagnetic signal sensing system, and more particularly, to an electromagnetic signal sensing system without interfering with the electromagnetic signal to be measured.
(B) Description of the Related Art
Since a wireless communication system uses an antenna to transmit and receive an electromagnetic signal, how to make the electromagnetic field emitted by the antenna comply with the specifications is an important subject for improving the antenna quality. In addition, the intensity of the electromagnetic wave emitted by the wireless communication product must be lower than the specific absorption rate (SAR) specified by the international safety standard to come into the market, therefore the SAR measurement technique is very important for the development of the cell phone. Presently, there are many electromagnetic wave measurement techniques; one of them utilizes the modulated scatterer to measure the distribution of the electromagnetic field.
U.S. Pat. No. 4,552,151 and U.S. Pat. No. 5,430,369 disclose a modulated scatterer array, which utilizes an electrical signal to modulate a diode inside the scatterer and incorporates with the fast scan to measure the electromagnetic field. The technique disclosed by the above-described patents applies the bias voltage to the diode inside the scatterer through a conductive wire. The conductive wire used for transmitting the electrical modulating signal will irradiate the electromagnetic wave, which however interferes with the electromagnetic signal to be measured. Briefly, the measurement accuracy of the electromagnetic signal is affected since the prior art uses the conductive wire to transmit the electrical modulating signal and electronically applies bias voltage to the diode inside the scatterer.